1. Field of Invention
The present invention relates to a radioactive material for inhibiting cancer and a preparation method thereof, especially to a radioactive material containing chitosan for inhibiting cancer and a preparation method thereof that are applied to fields of cancer cells and tumor inhibition.
2. Description of Related Art
According to statistics of Department of Health in 2006, most of leading causes of death in Taiwan relates to tumors and cancer has become the top leading cause of death for 25 years. For cancers, the main types of treatment include surgery, chemotherapy, and radiation therapy. Although surgery can remove tumors and tumor-like lesions, it has restricted applications in tumor metastasis and hematological malignancy. As to the chemotherapy, it uses chemical substances as drugs to treat disease. Patients require different treatment planning according to their physical strength, tumor size and stages. The chemotherapy can be applied alone, before the surgery, or in combinations with the radiation therapy. Yet it has toxicity for human tissue cells and severe side effects. Due to stereotactic location and progress of computer software, the radiation therapy gives good local control of the tumors and further increases the cure rate. But it such treatment still has acute or chronic side effects such as fatigue, infection, anemia, decreased appetite and dehydration etc. By drug specificity in uncontrolled cell division of tumor cells, the chemotherapy blocks progression in cell growth phase so that tumor cell division and proliferation are inhibited and the tumor cell apoptosis is enhanced. However, such kind of drug response affects all rapidly dividing cells in general. Not only tumor cells, the drugs also kill normal cells that divide quickly such as hair follicle cells, gastrointestinal lining and hematopoietic cells in bone marrow so that is has cytotoxic effect. Along with quick development of tumor molecular biology and genomic medicine, cancer diagnosis and treatment have a lot of new discoveries. Thus the most important issue in cancer therapy is how to blocks growth and proliferation of tumor cells directly without affecting normal cells.
The applications of external materials in medical use is firstly seen in hard tissue repair. The official record in medical literature starts from the middle of 16 century. Some people use iron wire for repairing fracture, silver wire for fixing fragments in long bone fracture, and metallic plate for fracture repair. After 1988, a new technology—human tissue engineering is provided. According to principles of cell biology and engineering, tissues cells in vivo are separated to be cultured and proliferated in vitro and then are implanted into scaffolds made from degradable biomedical materials. The scaffold is implanted into damaged tissues or organs. Along with cell secretion of matrix and degradation of biomedical material, a new tissue or organ with original morphology functions is formed. Thus the purposes of tissue repair and function reconstruction are achieved. In accordance with the material being used, biomedical material includes polymer (both artificial and natural), metals, ceramics and composite materials. The polymer materials are generally applied to surface devices, external communicating devices, and implant devices. The biocompatibility assessment of the biomedical materials such as such as cytotoxicity tests, sensitization tests, intracutaneous reactivity tests, systemic toxicity, tests for genotoxicity, hemolysis, carcinogenicity, reproductive toxicity, and biodegradability are required, based on type and duration of contact. A good biomedical material has the following features: (1) medical functions (2) biocompatibility (3) biological stability (4) market competitiveness.
The natural polymer that is degraded by enzymes in bodies shows quite good biocompatibility and includes fibrin, collagen, gelatin, hyaluronic acid, chitosan, and alginate extracted from plants. Chitosan is produced by deacetylation of chitin with high-concentrated hot alkali so that the acetyl group in chitin is removed and turned into the amino group. Chitosan is a linear polysaccharide composed of randomly distributed β-(1-4)-linked D-glucosamine (deacetylated unit) and N-acetyl-D-glucosamine (acetylated unit) and chemical formula of chitosan is shown in FIG. 1. Chitosan is positively charged and soluble in acidic solution (pH<6.5). Due to high-reactive amino group, chitosan is often converted into derivatives. Chitosan will not induce allergic reaction and rejection so it has good biocompatibility with tissues. After being degraded by enzymes, nontoxic aminosaccharides are generated and are absorbed without side effects. Moreover, chitosan is featured on antimicrobial activity and removal of toxic metal, broadly applied to medical filed. Thus chitosan, as natural polymer, has received much attention recently. It can be produced into micron/nano-scale particles used as carriers for drugs or applied to wound dressing material, artificial livers, bone and joint repair, nerve repair, and antimicrobial material.
There is no tumor inhibitor or cancer drugs formed by combination of chitosan and radioactive nuclide available now. Some tumor inhibitors or drugs are applied to the affected area through intravenous injections so that the drug requires no clot formation in blood. Moreover, before arriving the affected area, part of drugs is absorbed or interfered by human tissues so that the treatment response and clinical effect are dramatically reduced.
In order to overcome the above shortcomings, the present invention provides a radioactive material containing chitosan for inhibiting cancer and a preparation method thereof that treat cancers or tumors by means of succinimidyl 3,6-diaza-5-oxo-3-[2-((triphenylmethyl)thio)ethyl]-8-[(triphenylmethyl)thio]octanoate (SOCTA) connected with radionuclides and chitosan. Moreover, by features of clotting in alkaline environment of human blood and good biocompatibility of chitosan, the radioactive material containing chitosan is injected directly to the affected area and staying for a long term so as to effectively inhibit cancer cells or tumors. Thus the shortcomings of conventional drugs such as poor treatment response and clinical effect are overcome.